import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int a,b,c,d,e;
        a = in.nextInt();
        b = in.nextInt();
        c = in.nextInt();
        d = in.nextInt();
        e = in.nextInt();
        RR rr = new RR();
        double dd = rr.fun(a,b,c,d,e);
        System.out.printf("%.2f",dd);
    }
}
class RR{
    int a;
    int b;
    int c;
    int d;
    int e;
    public double fun(int a,int b,int c,int d,int e){
        double avg = (a+b+c+d+e)/5.0;
        return avg;
    }

}